(1) Field of the Invention
This invention relates to a fuel injection valve-adapted to inject a swirl flow of a high-pressure fuel from an injection port thereof.
(2) Description of the Related Art
The related art fuel injection valves include a fuel injection valve adapted to inject a high-pressure fuel directly into a combustion chamber of an internal combustion engine. As an example of this type of fuel injection valve, a fuel injection valve adapted to generate a swirl flow (a whirling flow or a vortex flow) in a high-pressure fuel, and inject the resultant fuel from an injection port so as to atomize fuel spray and increase a spray angle is known (refer to, for example, Japanese Patent Laid-Open No. 158989/1996).
The inventors of the present invention attempted to provide at an outlet portion of a fuel injection port of the same fuel injection valve as is taken as an example above with an inclined surface extending divergently in the fuel injection direction, for the purpose of further increasing a spray angle. However, according to this fuel injection valve made by way of trial, it was ascertained that the fuel spray interfered with an inlet valve, an exhaust valve and a spark plug due to restrictions placed on the mounting position of the fuel injection valve.
The inventors of the present invention then discussed the cause of this inconvenience to discover that the injection port having a cylindrical shape caused a cross-section of an atomized fuel injected from the injection port, i.e., a cross section, which is perpendicular to the fuel injection direction, of the fuel spray injected from the injection port to become right circular, and that this caused the inconvenience to occur. It was also discovered that, when the injection port was formed to a flattened shape over the whole length thereof so as to eliminate this inconvenience, the turning force of a swirl flow in the injection port was attenuated.
The present invention has been made in view of the above-mentioned circumstances, and provides on the basis of the above knowledge a fuel injection valve capable of eliminating the above-described inconvenience by a simple structure.
The fuel injection valve according to the present invention is a fuel injection valve adapted to inject a swirl flow of a high-pressure fuel from an injection port thereof, characterized in that the injection port includes a fuel inlet portion and a fuel outlet portion, the fuel inlet portion having a cylindrical bore, the fuel outlet portion having a cross-sectionally elliptic chamfered part, the chamfered part being joined at a circumference of an inlet thereof to a circumference of an outlet of the cylindrical bore, the chamfered part being formed so as to diverge from the inlet thereof to the outlet thereof.
In the fuel injection valve according to the present invention, a swirl flow of a high-pressure fuel is injected in the form of fuel spray into a combustion chamber of an internal combustion engine as the swirl flow is turned continuously along a circumferential surface of the cylindrical bore of the injection port and a circumferential surface of the chamfered part. During this time, a cross section, which is perpendicular to the injection direction, of the fuel spray injected from the injection port becomes elliptic due to the chamfered part of the fuel outlet portion.
Therefore, when an inlet valve, an exhaust valve and a spark plug are provided on the side of a shorter diameter portion of the elliptic cross section of the fuel spray, it becomes possible to prevent the fuel spray from interfering with the inlet valve, the exhaust valve and the spark plug while increasing a spray angle, and the attenuation of the turning force of the swirl flow is held down.